Apparatus, such as that disclosed in U.S. Pat. No. 3,664,791 granted to G. W. Brown on May 23, 1972, has been provided heretofore for successively delivering a heated thermoplastic sheet to a sheet heating station and then to a forming station at which opposed molds engage the sheet to differentially pressure form articles in the sheet. Apparatus constructed according to the present invention is particularly directed to new and novel apparatus for trimming articles, such as that disclosed in the aforementioned Brown patent, from the plastic sheet.
Prior art trim presses have included one stationary platen and one movable platen mounting opposed trim dies which engage opposite sides of the sheet to trim the article from the sheet. Such trim presses are not dynamically balanced and thus, the maximum speed of operation and output are limited. Accordingly, it is an object of the present invention to provide a new and novel trim press including dynamically balanced platens which concurrently move toward and away from each other to engage opposite sides of a sheet of thermoplastic material and sever an article formed in the sheet of material.
It is another object of the present invention to provide a trim press having an increased production rate.
It is another object of the present invention to provide a trim press having a pair of moving, dynamically balanced, trim die members and new and novel receiving apparatus for receiving the severed parts from one of the moving platens.
Another object of the present invention is to provide a new and novel trim press including a pair of dynamically balanced, movable platens, and a stationary receiver member for receiving the severed articles from one of the moving platens.
The apparatus constructed according to the present invention includes mechanism for successively indexing the plastic sheet through a trim station at which articles formed in the sheet are successively severed from the sheet, thus leaving a series of holes in the sheet which is thereafter moved downstream to a sheet severing station at which the sheet is cut into strips for scrap. Apparatus constructed according to the present invention includes a trim knife at the sheet severing station which engages the sheet, downstream of the trim station to cut the sheet into strips. If the trim knife at the sheet severing station engages the sheet at the same time that the trim die members engage the sheet at the trim station, the clamping of the sheet by the sheet severing knife at the sheet severing station will sometimes move the sheet and prevent accurate, final location of the sheet at the first trim station and thus result in inaccurate trimming of the articles. Accordingly, it is a further object of the present invention to provide cut-off knife mechanism at a sheet severing station downstream of a trim station for cutting the sheet into strips and mechanism for operating the trim knife at the sheet severing station in timed relation with operation of the trim dies at the trim station so that the trim knife engages the sheet a predetermined time after the trim dies sever the articles from the sheet at the trim station.
Other objects and advantages of the present invention will become apparent to those of ordinary skill in the art as the description thereof proceeds.